Protective device with metering and oscillography

ABSTRACT

A device, such as an intelligent electronic device (IED), provides a monitoring and protective function for a power system. The protective function uses stimulus acquired from the power system to detect power system conditions and to take one or more protective actions responsive thereto. The device may detect arc flash events in the power system based upon electro-optical and/or current stimulus measurements obtained therefrom. The stimulus measurements may be recorded to use in metering, validation, identifying detector misoperation, and/or event oscillography.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C §119(e) of U.S.Provisional Patent Application Ser. No. 61/098,636, entitled “LightDetecting Protective Device with Metering and Oscillography,” which wasfiled Sep. 19, 2008, and is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

This disclosure relates to power system monitoring and protection and,in particular, to oscillography and metering of power system stimuli.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various exemplary embodiments ofthe present system and method and are a part of the specification.Together with the following description, the drawings demonstrate andexplain the principles of the present system and method. The illustratedembodiments are examples of the present system and method and do notlimit the scope thereof.

FIG. 1A is a diagram of a power system comprising an arc flash detectionunit.

FIG. 1B is a diagram of a power system comprising an intelligentelectronic device and an arc flash detection unit.

FIG. 2 is a block diagram of one embodiment of a protective device withoscillography.

FIG. 3 is an example of a graphical display for oscillography data.

FIG. 4 is a block diagram of one embodiment of a protective device withmetering.

FIG. 5 is a flow diagram of one embodiment of a method for providingprotective functions with metering and oscillography.

DETAILED DESCRIPTION

Arc flashes pose a serious risk to both personnel and equipment in thevicinity of a flash. An arc flash may produce intense electro-optical(EO) radiation (including visible light) in the area of the arc. Inaddition, an overcurrent condition may be created on electricconductor(s) that feed the arc.

An arc flash detection unit (AFDU) may be configured to monitor aportion of a power system (e.g., an enclosure, housing, or the like).The AFDU may be configured to detect an arc flash event based onstimulus received from the power system. The AFDU may make use ofvarious different types of stimulus including, but not limited to: EOradiation detected in the vicinity of the power system, current levelswithin the power system, voltage levels at various points within thepower system, heat, chemical detection, pressure differentials (e.g.,sound), detection of particulates within an enclosure, or the like.

The time required to detect an arc flash event by a protection system(e.g., an AFDU) may be used to determine a total time required to clearthe arc flash (e.g., the total time required to clear the arc flash maybe a sum of the time required to detect the flash plus the time requiredto trip protective elements responsive to the detection). The timerequired to clear the arc flash may be referred to as a “total arcingtime,” which may be used to calculate the incident energy released bythe arc flash event (given the arc current, resistance, conductor gap,and the like). The detection time of an arc flash protection system mayvary depending upon the configuration of the protection system (e.g.,the sensitivity of the system). System sensitivity may be selected toprovide a balance between providing adequate arc flash protection andpreventing misoperation (e.g., detecting false positives).

The “Guide for Performing Arc Flash Hazard Calculations,” which ispromulgated by the Institute of Electrical and Electronics Engineers(IEEE) as IEEE 1584, provides several means for calculating arc flashincident energy, one of which is provided below in Equation 1:

Log(E _(N))=K ₁ +K ₂+1.0811·Log(I _(a))+0.0011·G  Eq. 1

In Equation 1, E_(N) is the arc flash incident energy, K₁ is aswitchgear-dependent constant value (depending upon whether theswitchgear is in an open or box configuration), K₂ is a constant (0 forungrounded or high-resistance grounded switchgear and −0.113 forgrounded systems), I_(a) is the maximum arcing current, and G is a gapbetween conductors within the switchgear.

The IEEE 1584 standard further provides means for determining anarc-protection boundary as follows:

$\begin{matrix}{D_{b} = \left\lbrack {4.184 \cdot C_{f} \cdot E_{n} \cdot \left( \frac{t}{0.2} \right) \cdot \left( \frac{610^{x}}{E_{b}} \right)} \right\rbrack^{\frac{1}{x}}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

In Equation 2, D_(b) is the distance of the boundary from the arcingpoint, C_(f) is a voltage constant (1.0 for voltages above 1 kV), E_(n)is the normalized arc flash incident energy (e.g., calculated perEquation 1 above), E_(b) is the incident energy at the boundary (5.0J/cm² for bare skin), and x is a distance exponent constant (0.973 for 5kV switchgear).

The protection boundary may determine where maintenance personnel maysafely work in relation to the switchgear and/or may determine what, ifany, protective gear should be used by the personnel.

Other standards exist for calculating arc flash energy to determineappropriate proximity and/or protective gear requirements. For instance,the National Fire Protection Association (NFPA) provides for thecalculation of an arc thermal performance value (ATPV), which is similarto the IEEE 1584 arc flash incident energy. The ATPV may determine aproximity boundary in which maintenance personnel may safely work. Inaddition, the ATPV and proximity boundary may indicate the nature of theprotective gear that should be used by personnel. Other arc flashsafety-related standards are provided by the National Electric Code(NEC) and Occupational Safety and Health Administration (OSHA).

FIG. 1A shows one embodiment of an AFDU 103 in an electrical powersystem 100. The AFDU 103 may be communicatively coupled to portions ofthe power system 100 to receive stimulus 120 therefrom. As will bediscussed below, the AFDU 103 may be configured to detect an arc flashevent occurring within the power system 100 (e.g., within a housing 104)based on the stimulus 120. The stimulus 120 may include currentmeasurements, EO radiation measurements, and the like.

In some embodiments, the AFDU 103 may be communicatively coupled to oneor more current transformers, or other measurement devices, configuredto provide the AFDU 103 with stimulus 120 comprising currentmeasurements from various points within the power system 100 (e.g., oneither side of a housing 104 in the electrical power system 100). Thehousing 104 may include components that may be susceptible to arc flashevents (e.g., switchgear, circuit breakers, and the like).

The AFDU 103 may be configured to receive other types of stimulus 120,such as measurements of EO radiation detected by one or more EOradiation collectors disposed within the vicinity of the power system100. The EO radiation collectors may be disposed within the housing 104and/or may be positioned to capture EO radiation produced by an arcflash event. In some embodiments, the EO radiation collectors may bepositioned within a switchgear enclosure 105 within the housing 104.

Although particular types of stimulus 120 are discussed herein (e.g.,current and EO stimulus), the AFDU 103 could be configured to detect anarc flash event based on any number of different types of stimulus 120.Therefore, this disclosure should not be read as limited in this regard.

The AFDU 103 may be configured to invoke certain protective functionsupon detecting an arc flash event. The protective function may beinvoked via a communications interface 121 with the power system 100(e.g., with power system components within the housing 104). Forexample, the AFDU 103 may trigger a circuit breaker, a switch, or otherequipment to remove an arcing circuit from power and/or isolate thecircuit from the rest of the power system 100. Alternatively, or inaddition, the AFDU 103 may produce an alarm signal that may be receivedby another protective system (e.g., a protective relay, an IED, or thelike), which may be configured to take one or more protective actionsresponsive to the alarm. The alarm may be transmitted to other remotedevices and/or may be made available for display on a human-machineinterface (HMI). These protective actions may reduce the amount ofenergy released by the arc flash event and/or may alert other systemsand/or personnel to the arc flash event.

The AFDU 103 may comprise and/or be communicatively coupled to a datastore 140, which may comprise computer-readable storage media, such ashard discs, Flash memory, optical storage media, tape media, and thelike. The AFDU 103 may store reporting and/or monitoring information inthe data store. In some embodiments, the AFDU 103 may be configured tostore quantized analog measurements of the stimulus 120 received fromthe power system. Upon detecting an arc flash event, a report may begenerated and stored in the data store 140. The report may include thestimulus 120 that caused the AFDU 103 to detect the arc flash event, mayinclude a record of the protective actions taken by the AFDU (or otherprotective devices), may include the messages transmitted and/orreceived via the communications interface 121, may include a responsetime of various protective devices within the power system (e.g., theresponse time of breakers, etc.), and the like.

FIG. 1B shows an electrical power system 101 that includes anintelligent electronic device (IED) 102 comprising an AFDU 103. The IED102 may provide various monitoring and protection services to the powersystem 101, including electrical power system components within ahousing 104.

As used herein, an IED (such as the IED 102 of FIG. 1) may refer to anyone or combination of: a CPU-based relay and/or protective relay, adigital fault recorder, a phasor measurement unit (PMU), a phasormeasurement and control unit (PMCU), a phasor data concentrator (PDC), awide area control system (WACS), a relay with phasor measurementcapabilities, a wide area protection system (WAPS), a SupervisoryControl and Data Acquisition (SCADA) system, a Programmable AutomationController (PAC), a Programmable Logic Controller (PLC), a dedicated arcflash protection controller (e.g., an AFDU), a system integrityprotection scheme, or any other device capable of monitoring and/orprotecting an electrical power system. Accordingly, the IED 102 maycomprise one or more processors, memories, computer-readable storagemedia, communications interfaces, HMI components, and the like. In theFIG. 1B embodiment, the IED 102 may be a protective relay, such as theSEL 751 manufactured by and available from Schweitzer EngineeringLaboratories, Inc. of Pullman, Wash.

As shown in FIG. 1B, the AFDU 103 may be implemented within the IED 102(e.g., as a component of the IED 102). The AFDU 103 may be implementedas machine-readable and/or machine-interpretable instructions stored ona computer-readable storage media of the IED 102. Alternatively, or inaddition, the AFDU 103 may comprise one or more hardware components. Insome embodiments, the AFDU 103 (or portions thereof) may be implementedindependently of an IED 102 (e.g., the AFDU 103 may comprise its ownindependent processing resources, communications interfaces, etc.).

The IED 102 and/or AFDU 103 may be configured to monitor power systemequipment disposed within the housing 104. The housing 104 may comprisea switchgear cabinet, a sealed enclosure, or any other housing type. Thehousing 104 may enclose switchgear equipment, such as circuit breakers110A, 110B, and/or 110C, and the like.

The AFDU 103 may receive various types of stimulus 120 from the powersystem 101. The stimulus 120 may be received directly (e.g., by sensorscoupled to the AFDU 103) and/or indirectly through another device, suchas the IED 102. In the FIG. 1B example, the AFDU 103 is configured toreceive current stimulus (current measurements obtained by currenttransformers) and EO stimulus (EO radiation captured by EO radiationcollectors). The AFDU 103 may be configured to detect an arc flash eventbased on the current and EO stimulus 120. However, in alternativeembodiments, the AFDU 103 may be configured to detect arc flash eventsusing other stimulus types (e.g., EO radiation and/or currentmeasurements alone, heat, pressure, chemical emissions, etc.).

The AFDU 103 may be configured to monitor a three-phase power signalcomprising three conductors 114A, 114B, and 114C, each of which may runthrough the housing 104 (one for each phase of the three-phase powersignal). For instance, the conductor 114A may carry an “A phase”electrical power signal, the conductor 114B may carry a “B phase”electrical power signal, and the conductor 114C may carry a “C phase”electrical power signal. Although a three-phase power signal is referredto herein, one skilled in the art will recognize that the teachings ofthis disclosure could be applied to power systems comprising any typeand/or number of power signals, and, as such, the teachings of thedisclosure should not be read as limited in this regard.

In the FIG. 1B example, the AFDU 103 receives current measurements fromcurrent transformers (CTs) communicatively and/or electrically coupledto the conductors 114A, 114B, and/or 114C; CTs 112A, 112B, and 112C arecoupled to the conductors 114A, 114B, and 114C at a first location 109,and CTs 108A, 108B, and 108C are coupled to the conductors 114A, 114B,and 114C at a second location 111 (e.g., on an opposite end of thehousing 104).

The AFDU 103 is communicatively coupled to EO radiation collectors 116A,116B, 116C, 116D, and 118, which may be configured to detect EOradiation emitted within the vicinity of the housing 104. As usedherein, an EO radiation collector, such as the point EO radiationcollectors 116A, 116B, and 116C, and 116D and/or the loop 118, may beconfigured to capture various types of EO radiation including visible EOradiation (e.g., visible light), infra-red (IR) radiation, ultra-violet(UV) radiation, and/or EO radiation at other wavelengths. Moreover, asused herein, light or a “light event” may refer to EO radiation thatcomprises EO energy at many different wavelengths, some of which may bevisible to the human eye and some of which may not. Therefore, thisdisclosure should not be read as limited to detection and/or processingof only EO radiation visible to humans, but should be read asencompassing any type of EO radiation known in the art.

The EO radiation collectors 116A, 116B, 116C, 116D, and 118 may bedistributed within the housing 104 and may be communicatively and/orelectro-optically coupled to the IED 102 and/or AFDU 103. In someembodiments, the detectors 116A, 116B, 116C and/or 116D may be “pointdetectors,” comprising fiber-optic leads (or other EO conductivematerial) configured to selectively detect EO radiation within thehousing 104 (e.g., detect EO radiation at particular points and/orlocations within the housing 104). The point detectors 116A, 116B, 116C,and/or 116D may be placed and/or positioned within the housing 104 so asto be capable of collecting EO radiation produced by an arc flash eventtherein (e.g., in the vicinity of the switchgear components, such as thecircuit breakers 110A, 110B, and/or 110C, a breaker trunk compartment(not shown), or the like). For example, the point detectors 116A, 116B,116C, and/or 116D may be positioned to have a line-of-sight and/or anelectro-optical path to respective breakers 110A, 110B, and/or 110C(e.g., to avoid “shadows” or other obscuring structures within thehousing 104). In some embodiments, the point detectors 116A, 116B, 116C,and/or 116D may be optically coupled to additional optical elements (notshown), such as mirrors, fiber-optic leads, lenses, EO conductivematerials, or the like, which may be configured to direct EO radiationproduced within the housing 104 and/or in the vicinity of the switchgearcomponents (e.g., breakers 110A, 110B, and/or 110C) to one or more ofthe detectors 116A, 116B, 116C, and/or 116D.

The detectors 116A, 116B, 116C, and/or 116D may comprise EO conductivematerials, such as fiber-optic filaments, capable of collecting EOradiation and transmitting a portion thereof to the IED 102 and/or AFDU103. Alternatively, or in addition, the EO radiation collectors 116A,116B, 116C, 116D may be capable of collecting EO radiation andtransmitting an electrical signal and/or other indicator of the detectedEO radiation to the IED 102 and/or AFDU 103 (e.g., via a communicationnetwork or the like).

The AFDU 103 may be coupled to other devices capable of collecting EOradiation, such as the loop EO radiation collector 118, which may extendthrough a portion of the housing 104. The loop EO radiation collector118 may comprise one or more sheathed fiber-optic cables (or other EOconductive material), wherein portions of the cable are exposed (e.g.,portions of sheathing around the EO conductive material are removed).The loop EO radiation collector 118 may be configured to receive EOradiation through these exposed portions. The EO radiation so receivedmay be transmitted to the IED 102 and/or AFDU 103. Alternatively, or inaddition, the loop EO radiation collector 118 may comprise a dedicatedEO radiation collector (not shown), which may transmit an electricalsignal or other indicator of the EO radiation detected thereby (e.g.,via a communication network or the like).

Although FIG. 1B depicts the AFDU 103 receiving EO stimulus from aparticular set of EO radiation collectors 116A, 116B, 116C, 116D, and118, one skilled in the art will recognize that the teachings of thisdisclosure could be applied to any number and/or type of EO radiationcollectors, including, but not limited to: Charge-Coupled Device (CCD)detectors, IR detectors, or the like. Therefore, this disclosure shouldnot be read as limited to any particular number, type, and/orarrangement of EO radiation collectors. Moreover, although a particularhousing 104 is depicted, the disclosure is not limited in this regard;the teachings of this disclosure could be applied to any housing knownin the art including, but not limited to: a breaker box, switch box,busbar enclosure, duct, conduit, or other enclosure or housing type.

The AFDU 103 may be configured to detect an arc flash event based oninter alia stimulus received from the CTs 108A, 108B, 108C, 112A, 112B,and 112C and/or EO radiation collectors 116A, 116B, 116C, 116D, and 118.High-levels of EO radiation and/or high current levels may be indicativeof an arc flash event occurring within the housing 104. Responsive tothe AFDU 103 detecting an arc flash event, the IED 102 may be configuredto take one or more protective actions, such as tripping one or morecircuit breakers (e.g., breakers 106A, 106B, and/or 106C), removing oneor more of the conductors 114A, 114B, and/or 114C from power,transmitting one or more alarm signals to external devices, displayingan alarm on an HMI, or the like.

For example, the IED 102 may be communicatively coupled to the circuitbreakers 106A, 106B, 106C via a communication network (e.g., over anEthernet network, a SCADA network, an IEEE C37.118 network, a wirelessnetwork, or the like). Responsive to the AFDU 103 detecting an arc-flashevent on one or more of the conductors 114A, 114B, and/or 114C, the IED102 may be configured to interrupt the power flow thereon.

As discussed above, the IED 102 and/or AFDU 103 may comprise and/or becommunicatively coupled to a data store 140. The data store 140 may beused to store monitoring information. For example, the stimulus receivedbefore and during the timeframe in which the AFDU 103 detected an arcflash event may be stored on the data store 140. The stimulus mayinclude EO radiation stimulus (EO measurements), current stimulus, orother stimulus types. The stimulus may be ordered and/or time-stampedwithin the data store 140. The time the AFDU 103 detected an arc flashevent may also be recorded, along with information regarding the actionstaken by the IED 102 and/or AFDU 103 responsive to the detecting (e.g.,breaker trip commands, response times, and the like). Accordingly, thereporting information stored on the data store 140 may allow the stateof the power system 101 leading up, during, and following an arc flashevent (or false arc flash detection) to be reconstructed.

In some embodiments, the data store 140 may store metering informationsuch as the intensity level of the stimulus received from variousdetector devices (e.g., the EO radiation collector devices 116A-116Dand/or 118). The metering information may aid in determining relevantsensitivity, cut off, and other thresholds used to supervise arc flashdetection by the AFDU 103 and/or IED 102.

FIG. 2 depicts a power system 200 comprising an AFDU 203. The AFDU 203depicted in FIG. 2 may be part of an IED, such as IED 102 depicted inFIG. 1B, and/or may be an independent device (e.g., add-on device),which may be communicatively coupled to an IED or other protectivedevice.

In the FIG. 2 embodiment, the AFDU 203 may monitor a portion of anelectrical power system 200, which may comprise a conductor 215 and acircuit breaker 206. The AFDU 203 may receive various types of stimulusfrom the electrical power system 200. In the FIG. 2 example, the AFDU203 receives current and EO radiation stimulus 220 via respectivedetector devices 213 and 217. A CT 213 may be coupled to the conductor215 to measure a current flowing thereon. The CT 213 may becommunicatively coupled to an input 211 of the AFDU 203 to providecurrent measurement stimulus thereto. An EO radiation collector 217 maybe placed in proximity to the conductor 215 and/or within a housing 204through which the conductor 215 passes. The EO radiation collector 217may comprise a point EO radiation collector, a loop EO radiationcollector, or any other device capable of collecting EO radiation.

An arc flash event occurring in the vicinity of the conductor 215 (e.g.,between the conductor 215 and ground, another conductor (not shown), aswitch (not shown), on a circuit breaker (not shown), or the like), mayproduce an EO event 250. The EO event 250 caused by the arc flash maycause EO radiation to be emitted, which may be detected by the EOradiation collector 217. As discussed above, the EO event 250 mayproduce EO radiation at various frequencies and/or wavelengths, some ofwhich may be visible to a human. The EO radiation collector 217 may beelectro-optically coupled to the AFDU 203 to transmit a portion of theEO radiation emitted by the EO event 250 and detected by the EOradiation collector 217 to the EO sensor 221 of the AFDU 203.

The EO sensor 221 may be configured to convert EO radiation receivedfrom the EO radiation collector 217 into a signal indicative of the EOradiation (e.g., an electrical signal). Accordingly, the EO sensor 221may comprise a photodiode (such as a silicon photodiode), a photoresistor, a CCD, a complementary metal-oxide-semiconductor (CMOS)device, or any other device or structure capable of converting EOradiation into an electrical signal.

In some embodiments, the signal produced by the EO sensor 221 may beamplified by an amplifier 222. The amplified measurements may bequantized (digitized) by a conversion element. In the FIG. 2 example,the conversion element may comprise an analog-to-digital converter 223,which may be configured to generate a quantized, discrete representationof the analog EO stimulus measurements. The amplifier 222 may comprise afixed or variable gain amplifier. In alternative embodiments, theamplifier 222 may be omitted.

Although FIG. 2 shows the EO sensor 221, amplifier 222, and A/Dconverter 223 as part of the AFDU 203, one skilled in the art willrecognize that these components could be disposed in proximity to the EOradiation collector 217. In this alternative embodiment, the EOradiation collector 217 may be configured to generate a signalindicative of detected EO radiation (e.g., as a sampled, discretemeasurement) using a local EO sensor, amplifier, and/or A/D converter(not shown), and could communicate the measurement(s) to the AFDU 203via a communication network (not shown) or the like.

The AFDU 203 includes an overlight element 224, which may produce an arclight signal 205 based on the EO measurements received via the EO sensor221. Assertion of the arc light signal 205 may indicate that the AFDU203 has detected EO radiation indicative of an arc flash event.

In some embodiments, the overlight element 224 may compare the sampled,discrete EO radiation measurements produced by the A/D converter 223 toan overlight threshold value. The overlight threshold value mayrepresent an EO radiation level that is indicative of an arc flash event(e.g., as opposed to changes in ambient light conditions or the like).The arc light signal 205 may be asserted if the EO radiation levelexceeds the threshold. The threshold may be adapted according to adesired sensitivity level of the AFDU 203.

The overlight element 224 may implement other comparison techniques. Insome embodiments, the overlight element 224 may implement atime-intensity metric, such as an inverse time-over-stimulus (e.g.,inverse time-over-light) metric, a cumulative stimulus metric, or thelike. Examples of such comparison techniques are described in co-pendingapplication Ser. No. 12/562,787 (attorney docket no. 08-030), filed 18Sep. 2009, and entitled “Secure Arc Flash Detection,” which is herebyincorporated by reference in its entirety.

Assertion of the arc light signal 205 may be indicative of an arc flashevent. Therefore, in some embodiments, the AFDU may assert the arc flashdetection signal 209 based upon the arc light signal 205 (e.g.,bypassing the AND gate 228). In the FIG. 2 example, however, the arcflash detection signal 209 is supervised by an arc current signal 207,which may be asserted based upon current stimulus (e.g., asserted upondetection of an overcurrent condition indicative of an arc flash eventas discussed below).

A current input 211 of the AFDU 203 may be configured to receive currentmeasurements acquired by a CT 213. The CT 213 may be communicativelyand/or electrically coupled to the conductor 215. Although the AFDU 203is shown as receiving a single current measurement, the disclosure isnot so limited; the AFDU 203 could be adapted to receive any number ofcurrent measurements from any number of current transformers.

In some embodiments, the current measurements may be filtered (by alow-pass, band-pass filter, anti-alias filter, a combination of filters,or the like). A quantized analog representation of the measurements maybe generated by an A/D converter 225. In addition, in some embodiments,a magnitude of the sampled current measurements may be calculated by anabsolute value block 226.

In the FIG. 2 example, the arc current signal 207 may be formed by acomparator 227, which may assert the arc current signal 207 if thecurrent measurements exceed an arc current threshold 208. However, thedisclosure is not limited in this regard; any comparison technique knownin the art could be used to assert the arc current signal 207.Furthermore, in some embodiments, the arc current signal 207 may beproduced using an overcurrent element (not shown), which may implement acumulative energy comparison technique as described above (e.g., aninverse time-over-stimulus metric, an accumulated stimulus metric, orthe like).

The arc light signal 205 and the arc current signal 207 flow to the ANDgate 228, the output of which may comprise an arc flash detection signal209. In some embodiments, the AFDU 203 may further include a securitytimer (not shown). The security timer may supervise the arc flashdetection signal 209, such that the arc flash detection signal 209 isasserted only if the output of the AND gate 228 is asserted for apre-determined time period and/or for a pre-determined number ofmeasurement cycles.

As discussed above, the arc flash detection signal 209 may cause one ormore protective actions to be performed. In some embodiments, the arcflash detection signal 209 may be used to activate one or moreprotective modules (e.g., protective modules and/or functions of an IED(now shown) upon which the AFDU 203 is implemented). FIG. 2 shows thearc flash detection signal 209 activating a trip signal module 229. Thetrip signal module 229 may comprise a protective function of aprotective device, such as an IED. Assertion of the arc flash detectionsignal 209 may cause the trip signal module 229 to generate a tripsignal to the circuit breaker 206. The circuit breaker 206 may removethe conductor 215 from power, which may clear the arc flash event andminimize the energy released thereby.

The AFDU 203 and/or the trip signal module 229 may be configured totransmit the arc flash detection signal in a particular format and/orusing a particular protocol, including, but not limited to: Ethernet,SCADA, IEEE C37.118, SNMP, or the like. As will be appreciated by one ofskill in the art, any signaling and/or control mechanism could be usedunder the teachings of this disclosure.

In some embodiments, the arc flash detection signal 209 may becommunicated to an IED or other device configured to monitor and/orprotect the power system 200. The AFDU 203 (alone or in conjunction withanother device, such as an IED) may be configured to provide other arcflash event monitoring and/or protection mechanisms including, but notlimited to: transmitting the arc flash detection signal 209 to an HMI,IED, or other device; tripping additional circuit breakers; divertingpower to or from portions of a power system; and the like.

In some embodiments, the AFDU 203 may be configurable. Configuring theAFDU 203 may comprise determining a sensitivity of the overlight element224, determining the sensitivity of the overcurrent element (not shown)and/or the threshold 208, determining how the arc flash detection signal209 is formed (e.g., by the arc light signal alone 205, by a combinationof the arc light signal 205 and the arc current signal 207, etc.), orthe like. The AFDU 203 may receive configuration information via acommunications interface (not shown) and/or an HMI 230. In embodimentsin which the AFDU 203 is implemented within an IED, the IED (or othercomputing device) may be configured to provide the 230 HMI or otherinterface to provide for configuration of the AFDU 203.

As discussed above, the stimulus received by the AFDU 203 may beavailable in a quantized analog format (from the A/D converters 223 and225). As used herein, quantized analog data (or “digital analog data”)may refer to a digital representation of an analog measurement, such asa digital representation of an EO radiation intensity measurement (e.g.,in LUX, lumens or the like), a current measurement (e.g., in amps), orthe like. The quantized analog measurements may be of varyingresolutions. The A/D converters 223 and 225 may be configured to outputdiscrete measurements of the EO and current stimulus at variousdifferent resolutions. In some embodiments, one or more of the A/Dconverters 223 and/or 225 may be configured to output measurements athigh resolution (e.g., to within one hundredth of an amp). In otherembodiments, a lower resolution may be used.

The AFDU 203 may include and/or be communicatively coupled to a datastore 240, which may include computer-readable storage media, such asdisc, Flash memory, optical storage, or the like. During monitoring, thequantized analog measurements output by the A/D converters may be storedin the data store 240. In some embodiments, the stimulus measurementsmay be stored in the order they are received (e.g., in a first-infirst-out (FIFO) data structure, or the like). The ordering may allowthe sequence of stimulus leading up to a particular event to bereconstructed (e.g., detection of an arc flash by the AFDU 203).Alternatively, or in addition, the measurements may include respectivetime stamp information (applied by the clock/timestamp module 242). Theinformation applied by the clock/timestamp module 242 may indicate atime each stimulus measurement was received. The clock/timestamp module242 may operate on an internal time standard. Alternatively, or inaddition, the clock/timestamp module 242 may be coupled to an externaltime source 244, such as IRIG (via GPS satellites), WWVB, WWB, a localcommon time source, or the like.

The data store 240 may be configured to record indicators of the arclight signal 205, the arc current signal 207, and/or the arc flashdetection signal 209. The signals 205, 207, and/or 209 may includerespective time stamps. The data store 240 may include additionalinformation regarding protective actions taken by the AFDU 203, such asthe operation of the trip signal module 229, any alarms asserted by theAFDU 203, alerts issued by the AFDU 203, and so on.

The information stored in the data store 240 may be made available to anoperator of the AFDU 203 and/or to other devices (e.g., an IED (notshown), other protective devices (not shown) or the like). In the FIG. 2example, the data store 240 may be coupled to the HMI 230 via a reportgenerator 246, which may be configured to present data stored in thedata store 240 to an operator. The report generation module 246 may beconfigured to retrieve and present stimulus data stored in the datastore 240. In some embodiments, the report generator 246 may be furtherconfigured to reconstruct a series of stimulus measurements (andresponses of the AFDU 203 thereto) over a particular timeframe, such asthe time leading up to detection by the AFDU 203 of an arc flash event.The reconstruction may allow an operator (through the HMI 230) toidentify the cause of the arc flash detection.

Data may be exported from the data store 240. The exporting may compriseretrieving from the data store 240 a particular sequence of quantizedanalog stimulus measurements, response information, and the like. Theinformation may be exported within a particular time frame (e.g.,stimulus measurements received on May 9, 2008, from 10 AM to 1 PM)and/or leading up to a particular event (e.g., stimulus measurementsrecorded in the hour leading up to detection of an arc flash event). Theexporting may be done through the HMI 230, a communication interface(not shown), an external storage interface (e.g., USB®, Firewire®, orother interface), or the like.

In some embodiments, the report generator 246 may make stimulusmeasurements available through the HMI 230 in real-time (e.g., as themeasurements are received). The real-time stimulus measurements mayallow an operator to meter and/or configure the system. For example, areal-time EO radiation measurement at particular times of day mayprovide an operator an indication of the ambient light conditions withinthe power system (e.g., as observed by the EO radiation collector 217).The operator may use the metering information to configure the AFDU 203appropriately (e.g., configure the overlight element 224 with a set ofthresholds, inverse time-over-light curve, or the like). Similarly, thereal-time measurements may be used in a testing and/or calibrationscenario. For example, an operator may cause EO radiation to be emittedin the vicinity of the EO radiation collector 217 and then determine(via the HMI 230) the resulting quantized analog measurements recordedby the AFDU 203. A difference between the intensity of the produced EOradiation and the EO radiation recorded by the AFDU 203 may be used todetermine the efficiency (e.g., attenuation) of the EO radiationcollector 217 and/or EO conductor cable 218.

The report generator 246 and/or HMI may be configured to display EOradiation stimulus measurements as a quantized analog measurement (e.g.,in LUX, lumens, LUX, or the like) and/or on a detector pickup percentagebasis. For instance, EO radiation stimulus may be displayed as 6000 LUXand/or, if the pickup of the EO radiation collector 217 and/or EO sensor221 is approximately 1200 LUX, the display may read 500% or as a pickupvalue of 5.

Other stimulus types may be similarly displayed. For instance, currentstimulus may be displayed in terms of the current magnitude (e.g., onthe conductor 215), the current magnitude on the current transformer 213(e.g., 1250 Amps), and/or a percentage (or per-unit) basis. The currentmagnitude may be displayed as a root mean square (RMS) value that may becalculated by the report generator 246. The percentage or per-unit basismay be based on the overcurrent threshold 208. Thus, if the current is80% of the threshold, the display may register a per-unit (or pickup)value of 0.8 for current. Alternatively, or in addition, the stimulusmeasurements (EO radiation, current, and the like) may be displayed interms of an energy level represented thereby. Alternatively, or inaddition, Equations 1 and 2, discussed above, may be applied to thestimulus data to display an estimated total energy produced by an arcflash event, provide proximity guidelines, protective gear requirements,and the like. Similarly, the EO sensor 221 and/or the AFDU 203 may beconfigured to estimate an energy represented by the EO radiationstimulus (e.g., by combining a spread spectrum of observed EO radiation,estimating an energy level from the observed EO radiation, properties ofthe EO radiation collector 217, EO sensor 221, and the like, and so on).The EO and current energy estimates may be used to refine the respectiveenergy estimates, provide cross-validation and/or error checking.

In other embodiments, the data store 240 and/or the report generatormodule 246 may be configured to record and provide access to otherstimulus types, such as voltage measurements, pressure measurements,temperature, chemical, and so on. Accordingly, this disclosure shouldnot be read as limited to recording only EO and/or current stimulus.

The report generation module 246 may have different capacity levelsdepending upon the monitoring needs and/or configuration of the AFDU 203(e.g., the frequency of the stimulus measurements, the resolution of theA/D converters 223 and 225, and so on). In some embodiments, the datastore 230 may have sufficient capacity to store hours, days, weeks, ormonths worth of monitoring data. In some embodiments, the data store 240may be communicatively coupled to a backup storage device (not shown),such as a network attached storage (NAS) device, an external data store(not shown) or the like. The AFDU 203 (through the HMI 230) may beconfigured to periodically backup and/or offload the contents of thedata storage module 240 to the backup storage device to prevent dataloss and/or to free up storage space on the data storage module 240 tothereby provide for continuous, uninterrupted recording.

The report generating module 246 and/or the HMI 230 may be configured todisplay report data in various different ways (e.g., in a table,graphically, or the like). FIG. 3 depicts one example of a graphicaldisplay of information recorded on the data store 240 and presented bythe report generator 246 via the HMI 230. The display 300 of FIG. 3includes a plot of stimulus measurements as a function of time. In theFIG. 3 example, the plot 300 depicts quantized analog current stimulusmeasurements 310 and EO radiation stimulus measurements 312 along a timeaxis 301. The current stimulus 310 may be displayed in terms of amperes,current transformer pickup, in proportion to an overcurrent threshold,or the like. The EO radiation stimulus 312 may be displayed in terms oflumens, LUX, in terms of a detector pickup value, in proportion to an EOthreshold, or the like.

The FIG. 3 example includes an arc flash detection signal 314. The arcflash detection signal 314 may correspond to the arc flash signal 209 ofFIG. 2, a breaker trip signal produced by the trip signal generator 229of FIG. 2, or another signal produced by an AFDU (or IED) responsive todetecting an arc flash event.

As illustrated in FIG. 3, the current 310 and EO radiation 312 stimulusremain relatively low until time t₀ 302, at which time an event occursthat causes EO radiation and overcurrent current stimulus to bereceived. At time t₁ 303, an arc flash detection signal is observed. Thetime difference between t₀ 302 and t₁ 303 may represent a response timeof the AFDU or IED.

Although FIG. 3 depicts a particular set of quantized analog stimulusmeasurements and an arc flash detection signal 314, the disclosure isnot limited in this regard. The graphical display of FIG. 3 could beadapted to include other quantized analog measurements (pressure,voltage, etc.), and/or other response signals (e.g., alarms, trippingsignals, or the like). Similarly, the display could be adapted todisplay the quantized analog stimulus measurements and/or responsesignals in alternative formats, using alternative interfaces (e.g.,graphical, audio, video, etc), and the like.

FIG. 4 is a block diagram of one embodiment of an IED configured toprovide EO radiation metering. The AFDU 403 of FIG. 4 may be implementedin conjunction with and/or separately from an IED, such as the IED 102of FIG. 1B.

The AFDU 403 may include a metering module 448, which may becommunicatively coupled to an HMI 430. The metering module 448 may beconfigured to receive quantized analog stimulus measurements, includingmeasurements of EO stimulus (received via EO radiation collector 217)and current measurements (received via current input 211). Although notshown in FIG. 4, the quantized analog stimulus measurements may be timestamped (e.g., by a clock/time stamp module (not shown)) and stored on adata store (not shown) for later retrieval and/or display using a reportgenerator module (not shown).

The metering module 448 may make quantized analog stimulus measurementsavailable as they are received (e.g., in real-time). The quantizedanalog stimulus measurements may be displayed to an operator on the HMI430 and/or transmitted to other devices and/or operators via acommunications interface (not shown). The quantized analog measurementdata may be displayed in terms of magnitudes, percentages, per-unitbasis, and the like (as described above). The metering module 448 mayfurther provide for the display of signals generated by the AFDU 403 (orother devices) responsive to the stimulus may be displayed, including,but not limited to: the arc light signal 205, the arc current signal,the arc flash detection signal 209, a tripping signal generated by thetrip signal module 229, and the like. In some embodiments, the displayprovided by HMI 430 may further include configuration parameters of theAFDU 403, such as the overcurrent threshold 208, the configuration ofthe overlight element (e.g., the inverse time-over-light curve), and thelike. The HMI 430 may allow an operator to adjust the configurationsettings responsive to the metering data (e.g., set the EO and/orovercurrent detection threshold(s) according to ambient lightingconditions and/or nominal operating conditions observed within the powersystem 400).

In some embodiments, the metering module 448 may be used to calibrateand/or validate the AFDU 403. For example, an EO emitter 450 may beconfigured to emit EO radiation in the vicinity of the EO radiationcollector 217. The EO emitter 450 may be configured to emit EO radiationin the vicinity of switchgear (or other power system components)monitored by the AFDU 403. The EO emitter 450 may be further configuredto emit EO radiation from a position within the switchgear, from whichEO radiation would likely be emitted in an actual arc flash event. Insome embodiments, EO emitter 450 may be controlled by a validationcomponent. Examples of such an EO emitter are disclosed in co-pendingapplication Ser. No. 12/562,197 (attorney docket no. 08-016), filed 18Sep. 2009, and entitled, “Validation of Arc Flash Detection Systems,”which is hereby incorporated by reference in its entirety.Alternatively, or in addition, the EO radiation collector 217 maycomprise an EO conductor (not shown) capable of transmitting EOradiation into the vicinity of the EO radiation collector 217 (e.g., foruse in a self test operation). Examples of such an EO radiationcollector are disclosed in co-pending application Ser. No. 12/562,834(attorney docket no. 08-031), filed 18 Sep. 2009, and entitled, “ArcFlash Protection with Self-Test,” which is hereby incorporated byreference in its entirety.

The metering module 448 may display and/or cause to be recorded,quantized analog EO radiation measurements received responsive to EOradiation emitted by the EO emitter 450. The measurements may be used toconfigure, test, and/or validate the operation of the AFDU 403. Forexample, if no EO radiation is detected by the EO radiation collector217 and/or transmitted via the EO conductor cable 218 (e.g., no EOradiation is received by the EO sensor 221), it may be determined thatthere is a problem with the EO radiation collector 217 (e.g., the EOradiation collector 217 is not positioned to receive the EO radiationemitted by the emitter 450, the EO radiation collector 217 is capable ofreceiving EO radiation, the EO conductor cable 218 is incapable oftransmitting EO radiation, or the like).

An attenuation level of the EO radiation collector 217 and/or EOconductor cable 218 may be determined by comparing the intensity of theEO radiation emitted by the EO emitter 450 to the quantized analog EOradiation measurements received at the AFDU 403. A high attenuationlevel may indicate that the EO radiation collector 217 and/or EOconductor cable 218 have been damaged. For instance, when an EOconductor (such as the EO conductor cable 218 and/or an loop EOradiation collector (described in the co-pending applicationsincorporated by reference above)) is abraded, it may begin to attenuateEO signals transmitted thereon. The attenuation may become progressivelyworse, until reaching a point that the EO conductor and/or EO radiationcollector are no longer capable of collecting and/or conducting EOradiation to the AFDU 403. Similarly, the detection area of an EOradiation collector may become progressively obscured over time (e.g.,by dust, grime, or the like) and/or may be gradually moved out of place(e.g., by vibrations within a switchgear enclosure). The metering of theAFDU 403 using quantized analog measurements as opposed to a binary “on”or “off” indication of EO transmission via the EO radiation collector217 may allow for detection of this progressive deterioration, which mayallow such issues to be addressed before a failure occurs.

The metering module 448 may be used to evaluate the configuration of theAFDU 403. For example, some EO radiation collectors 217 and/or EOconductor cables 218 may inherently attenuate signals transmittedthereon (e.g., a fiber optic cable may attenuate EO radiation at a ratebetween 0.5 dB/km to 1000 dB/km). The metering module 448 may allow anoperator (or other device) to determine the attenuation of a particularAFDU 403 configuration (e.g., using the quantized analog measurementsmade available by the metering module 448). If the attenuation imposedby the EO radiation collector 217 and/or EO conductor cable 218 is toogreat, the AFDU 403 may be reconfigured (e.g., to use a shorter EOconductor cable 218, to include an EO repeater (not shown), toincorporate a remote EO sensor (not shown), or the like).

The metering module 448 may also be used to determine an appropriateconfiguration for the AFDU 403 (e.g., for the threshold 208, the inversetime-over light curve used by the overlight element 224, and the like).For example, an operator may observe the quantized digital signalstimulus measurements made available by the metering module 448 (or thereport generator 246 described above) and set configuration of the AFDU403 accordingly (e.g., to be greater than observed ambient EO radiationlevels, nominal current levels, etc.). In embodiments, incorporating areporting module and/or data store (as in FIG. 2), the operator mayobserve changes to the ambient stimulus levels over time. For example,the levels of ambient EO radiation levels may change depending upon theorientation of the sun relative to the EO radiation collector 217 (e.g.,depending upon the time of day, the season, and the like). Similarly,current levels may change depending upon power demand on the powersystem (e.g., current levels may be greater during summer afternoonsthan evenings). The operator may configure the AFDU 403 accordingly(e.g., set thresholds according to the time of day, change the positionof detector(s) within the power system, and the like).

The operation of the metering module 448 may be controlled by anoperator via the HMI 430 and/or a communications interface. The operatormay control the types of quantized analog stimulus measurementsdisplayed via the HMI 430 (e.g., EO radiation, current, etc.), controlthe manner in which the stimulus measurements are displayed (e.g.,select a time scale, measurement factor (e.g., linear, logarithmic,etc.), select the responsive signals to be displayed, selectconfiguration parameters for display (e.g., threshold values, such asthe overcurrent threshold 208), and the like.

FIG. 5 is a flow diagram of one embodiment of a method for providing aprotective device with metering and oscillography. The method 500 maycomprise one or more machine executable instructions stored on acomputer-readable storage medium. The instructions may be configured tocause a machine, such as a computing device or IED, to perform themethod 500. In some embodiments, the instructions may be embodied as oneor more distinct software modules on the storage medium. One or more ofthe instructions and/or steps of method 500 may interact with one ormore hardware components, such as computer-readable storage media,communications interfaces, EO radiation collectors, EO emitters, and thelike. Accordingly, one or more of the steps of method 500 may be tied toparticular machine components.

At step 510, the method 500 may start and be initialized, which maycomprise allocating and/or initializing resources required by the method500, such as communications interfaces, detector devices,computer-readable storage media, and the like.

At step 520, a sequence of one or more of stimulus measurements may bereceived. The stimulus measurements may include EO radiationmeasurements, current measurements, voltage measurements, pressuremeasurements, or the like. The stimulus measurements received at step520 may be processed. For example, the stimulus measurements may befiltered to remove harmonic content and/or to isolate particularfrequencies and/or frequency ranges. In some embodiments, the processingmay include applying one or more compensation parameters to themeasurements to account for different detector types and/or detectorconfigurations (e.g., compensate for different orientation and/orwinding configurations of different current transformers, differentpickup thresholds of various EO radiation collectors, attenuation levelsof various transmission media, and the like).

At step 530, quantized analog representations of the stimulusmeasurements may be obtained. As discussed above, a quantized analogmeasurement representation may include a digital representation of ananalog stimulus measurement. The quantized analog representations may beproduced by a conversion element, such as A/D converter or othersampling and/or quantization device.

At step 540, the quantized analog representations may be stored in acomputer-readable storage medium. In some embodiments, the storagemedium may order the stimulus measurements in time (e.g., in a first-infirst-out orientation). Alternatively, or in addition, the quantizedanalog measurements may be associated with time stamp information, whichmay indicate a time each of the measurements was received. The timestamp information may be derived from an internal clock (e.g., a clockprovided by the method 500). In some embodiments, the clock may besynchronized to an external time source or reference time. The orderingand/or time stamping may allow the stimulus measurements received withina particular internal or timeframe to be reconstructed.

At step 550, and concurrently with step 540, the method 500 may performa monitoring function using the stimulus measurements. The monitoringfunction of step 550 may include arc flash detection as described above.At step 560, the method may determine whether any protective actions areto be taken responsive to the monitoring (e.g., determine whether an arcflash event has been detected). If protective actions are to be taken,the flow may continue to step 565; otherwise, the flow may continue tostep 590.

At step 565, one or more protective actions may be taken responsive tothe monitoring function of step 550. For example, step 565 may includeasserting an arc flash detection signal (e.g., asserting the arc flashdetection signal 207 discussed above in conjunction with FIGS. 2 and 4).The protective actions of step 565 may further include generating one ormore breaker tripping signals, asserting one or more alarms, issuing oneor more alerts, or the like.

At step 567, the information regarding the protective actions taken bythe method 500 may be recorded in a computer-readable medium. Asdiscussed above, the recording may include ordering the informationand/or applying time stamp data to the information. The ordering and/ortime stamp data may allow the protective actions to be correlated withthe quantized analog stimulus data recorded at step 540.

At step 570, the method 500 may provide the information stored on thecomputer-readable storage medium to an operator or process (via an HMI).The information may be provided by a report generator (such as thereport generator 246 of FIG. 2) and/or a metering module (such as themetering module 448 of FIG. 4). Accordingly, the method 500 may makeavailable quantized analog stimulus measurements recorded over aparticular time period (along with any protective actions takenresponsive thereto). Alternatively, or in addition, the method 500 maymake quantized analog stimulus measurements (and information regardingprotective actions taken responsive to the measurements) available on areal-time basis (as the stimulus measurements are received and/or as theprotective actions are taken). The information provided at step 570 maybe used to test, validate, calibrate, and/or configure the method 500 asdescribed above (e.g., identify detector issues, determine detectorattenuation, establish arc flash detection levels or thresholds,determine ambient stimulus levels, and so on).

At step 580, the method 500 may analyze the information recorded atsteps 540 and/or 565 to automatically detect potential problems in themethod 500. As discussed above, detecting devices, such as EO radiationcollectors, EO conductors, current transformers, and the like may besubject to gradual degradation (e.g., an EO conductor may be graduallyabraded and/or moved out of position by vibration within switchgearhousing, a current transformer may gradually break down, or the like).The analysis of step 580 may include determining detector attenuationbased upon recorded quantized analog stimulus measurements. For example,if an EO radiation collector exhibits a gradual decline in ambient EOradiation levels over a particular timeframe, step 580 may determinethat the EO radiation collector (or an EO conductor coupling the EOradiation collector to the method 500) may be subject to degradation.Similarly, if a current transformer exhibits inconsistent and/orvariable nominal measurements (over a particular timeframe), the method500 may identify a problem in the current transformer. Alternatively, orin addition, step 580 may include supplying stimulus to the method 500and observing the result. For example, the stimulus received at step 520may be of a known type and/or intensity (may be produced by the method500). The intensity of the stimulus may be compared against thequantized analog measurements determined responsive thereto. Anattenuation of the detector used to receive the stimulus may bedetermined by comparing the known intensity of stimulus provided to themethod 500 against the quantized analog stimulus measurements actuallyreceived by the method 500.

At step 585, the method 500 make take one or more protective actionsresponsive to the analysis of step 580. The protective actions of step585 may include issuing one or more alerts. Issuing an alert may includestoring the alert on a computer-readable medium, displaying the alert onan HMI, transmitting the alert via a communication interface coupled tothe method 500 (e.g., sent via email, SMS message, PSTN, etc.), or thelike. The alert may include information to identifying one or moredetectors that may be misoperating (according to the analysis of thequantized analog stimulus measurements of step 580). The information mayfurther indicate the nature of the suspected misoperation and/or asuspected cause thereof (e.g., high levels of attenuation in an EOconductor, etc.). The protective action(s) taken at step 585 may beselected according to a severity of the detector problem determined atstep 580. For example, in some embodiments, a protective action mayinclude tripping a breaker, issuing alerts to other protective devices,or the like. Such actions may be taken upon determining that aparticular detector (e.g., an EO radiation collector) is inoperable and,as such, the power system is unprotected.

At step 590, the method 500 may determine whether monitoring is tocontinue. If so, the flow may return to step 520 where stimulusmeasurements may be received; otherwise, the flow may terminate at step595.

The above description provides numerous specific details for a thoroughunderstanding of the embodiments described herein. However, those ofskill in the art will recognize that one or more of the specific detailsmay be omitted, or other methods, components, or materials may be used.In some cases, operations are not shown or described in detail.

Furthermore, the described features, operations, or characteristics maybe combined in any suitable manner in one or more embodiments. It willalso be readily understood that the order of the steps or actions of themethods described in connection with the embodiments disclosed may bechanged as would be apparent to those skilled in the art. Thus, anyorder in the drawings or Detailed Description is for illustrativepurposes only and is not meant to imply a required order, unlessspecified to require an order.

Embodiments may include various steps, which may be embodied inmachine-executable instructions to be executed by a general-purpose orspecial-purpose computer (or other electronic device). Alternatively,the steps may be performed by hardware components that include specificlogic for performing the steps, or by a combination of hardware,software, and/or firmware.

Embodiments may also be provided as a computer program product includinga computer-readable storage medium having stored instructions thereonthat may be used to program a computer (or other electronic device) toperform processes described herein. The computer-readable storage mediummay include, but is not limited to: hard drives, floppy diskettes,optical disks, CD-ROMs, DVD-ROMs, ROMs, RAMs, EPROMs, EEPROMs, magneticor optical cards, solid-state memory devices, or other types ofmedia/machine-readable storage media suitable for storing electronicinstructions.

As used herein, a software module or component may include any type ofcomputer instruction or computer executable code located within a memorydevice and/or computer-readable storage medium. A software module may,for instance, comprise one or more physical or logical blocks ofcomputer instructions, which may be organized as a routine, program,object, component, data structure, etc., that perform one or more tasksor implements particular abstract data types.

In certain embodiments, a particular software module may comprisedisparate instructions stored in different locations of a memory device,which together implement the described functionality of the module.Indeed, a module may comprise a single instruction or many instructions,and may be distributed over several different code segments, amongdifferent programs, and across several memory devices. Some embodimentsmay be practiced in a distributed computing environment where tasks areperformed by a remote processing device linked through a communicationsnetwork. In a distributed computing environment, software modules may belocated in local and/or remote memory storage devices. In addition, databeing tied or rendered together in a database record may be resident inthe same memory device, or across several memory devices, and may belinked together in fields of a record in a database across a network.

It will be understood by those having skill in the art that many changesmay be made to the details of the above-described embodiments withoutdeparting from the underlying principles of the invention.

1. An intelligent electronic device (IED) configured to provide aprotective function to a power system, comprising: a first inputconfigured to receive measurements of a first stimulus type from thepower system; a second input configured to receive measurements ofelectro-optical (EO) radiation from the power system; a conversionelement configured to determine quantized analog measurementscorresponding to the measurements received via the first and the secondinputs; a computer-readable storage medium configured to store thequantized analog measurements; and a data output configured to exportthe quantized analog measurements from the computer-readable storagemedium.
 2. The IED of claim 1, wherein the first input is configured toreceive current measurements acquired by a current transformercommunicatively coupled to the power system.
 3. The IED of claim 1,wherein the IED is configured to detect an arc flash event based uponthe measurements received via the first and the second inputs.
 4. TheIED of claim 3, wherein the IED is configured to take one or moreprotective actions responsive to detecting the arc flash event.
 5. TheIED of claim 4, wherein the one or more protective actions include oneof asserting an arc flash detection signal, tripping a circuit breaker,asserting an alarm, and issuing an alert.
 6. The IED of claim 4, whereindetection of the arc flash event is recorded in the computer-readablestorage medium.
 7. The IED of claim 1, further comprising ahuman-machine interface configured to display the quantized analogmeasurements to an operator.
 8. The IED of claim 7, wherein thequantized analog measurements are displayed on the human-machineinterface as they are determined by the conversion element.
 9. The IEDof claim 1, wherein the conversion element comprises an anlog-to-digitalconverter.
 10. The IED of claim 1, wherein the IED is configured tocause EO radiation to be emitted in the vicinity of an EO radiationcollector communicatively coupled to the second input, and wherein theIED is to determine an attenuation of the EO radiation collector basedupon quantized analog measurements determined from EO radiationmeasurements received responsive to the emitting.
 11. The IED of claim9, wherein the IED is configured to assert an alert if the attenuationexceeds a threshold.
 12. The IED of claim 11, wherein the detector alertis displayed on a human-machine interface communicatively coupled to theIED.
 13. The IED of claim 12, wherein the alert is recorded on thecomputer-readable storage medium.
 14. The IED of claim 1, furthercomprising a clock module configured to time stamp the quantized analogmeasurements.
 15. A method for protecting a power system, comprising:receiving measurements from the power system, the measurementscomprising measurements of a first type of stimulus acquired by a firstdetector and measurements of electro-optical (EO) radiation collected byan EO radiation detector; converting the received measurements intoquantized analog measurements comprising quantized analog measurementsof the first type of stimulus and quantized analog EO radiationmeasurements; recording the quantized analog measurements on acomputer-readable storage medium; providing a protective function usingthe measurements of the first type of stimulus and the measurements ofthe EO radiation; and exporting a portion of the quantized analogmeasurements.
 16. The method of claim 15, wherein the protectivefunction asserts an arc flash detection signal responsive to detectingan arc flash event based upon the EO radiation measurements.
 17. Themethod of claim 16, further comprising taking one or more protectiveactions when the arc flash detection signal is asserted, whereinindications of the one or more protective actions are recorded on thecomputer-readable storage medium.
 18. The method of claim 17, whereinone of the protective actions is tripping a circuit breaker, assertingan alarm, and issuing an alert.
 19. The method of claim 15, furthercomprising time stamping the quantized analog measurements recorded onthe computer-readable storage medium.
 20. The method of claim 19,further comprising reconstructing a sequence of quantized analog EOradiation measurements within a timeframe using the time stamps.
 21. Themethod of claim 19, wherein the first type of stimulus is currentstimulus acquired by a current transformer communicatively coupled tothe power system, and wherein the quantized analog stimulus measurementsinclude quantized analog current measurements, the method furthercomprising reconstructing a sequence of quantized analog currentmeasurements within the timeframe using the time stamps.
 22. The methodof claim 19, further comprising causing a sequence of time-stamped,quantized analog EO stimulus measurements to be presented on a displaydevice.
 23. The method of claim 15, further comprising causing quantizedanalog stimulus measurements to be displayed on a display device as thequantized analog stimulus measurements are received.
 24. The method ofclaim 15, further comprising: causing EO radiation to be emitted in thevicinity of the EO radiation collector; and determining an attenuationof the EO radiation collector based upon quantized analog EO radiationmeasurements determined responsive to the emitting.
 25. The method ofclaim 24, further comprising detecting a fault in the EO radiationcollector if the attenuation exceeds a threshold.
 26. Acomputer-readable storage medium comprising instructions, which, ifexecuted by an intelligent electronic device (IED), cause the IED toperform a method for protecting a power system, the method comprising:receiving stimulus measurements from a power system, the stimulusmeasurements comprising current stimulus measurements andelectro-optical (EO) radiation measurements; converting the stimulusmeasurements into quantized analog measurements comprising quantizedanalog current measurements and quantized analog EO radiationmeasurements; time stamping the quantized analog measurements; recordingthe time-stamped, quantized analog measurements on a computer-readablestorage medium; providing a protective function using the quantizedanalog measurements; and providing for displaying a sequence ofquantized analog measurements on a display device.